Process of preparing alkyl xanthic disulphides



Patented June 27, 1939 PATENT OFFICE PROCESS OF PREPARING XAN'IHIC DISULPHIDES August Mueller, Frankfort-on-the-Main-Griesheim, Germany, assignor to I. G. Farbenindustrie Aktiengesellschaft, Frankfort-on-the- Main, Germany No Drawing. Application March 11, 1937, Serial No. 130,308. In Germany 'March 14, 1936 4 Claims.

This invention relates to a process of preparing alkyl xanthic disulphides from xanthates of alkali metals.

It is known that by the oxidation in an aque- 5 ous solution xanthates may be transformed into alkyl xanthic disulphides and different methods have already been proposed therefor. Thus, for instance, alkyl xanthic disulphides may be obtained by the electrolytic oxidation of xanthates in an aqueous solution, but this process, from an industrial point of view, shows some difiiculties. Even platinum anodes are corroded and the yield of material and current dependent on the material of the electrodes, the purity of the solutions and other factors is very small. The alkyl xanthic disulphides formed at the anode are likewise not especially pure. The oxidation of the xanthate solutions with halogen compounds yields alkyl xanthic disulphides which are very much impurified with by-products, for instance with sulphur chloride when applying chlorine. Owing to the liability of the first formed xanthic acids to a readily decomposition the use of oxidizing agents only effective in an acid solution leads to very 5 bad yields also in a cooled solution. The oxidation of xanthate solutions by means of substances containing theoxygen bound in a peroxide-like manner has also proved to be a failure. Even the very active sodium peroxide is completely ineffective and hydrogen peroxide in a large excess likewise oxidizes only part of the xanthate present so as to obtain the alkyl xanthic disulphide.

Now I have found that persulphates which as regards their oxidizing power generally act in a manner similar to the above mentioned percompounds, contrary to these oxidize xanthate solutions surprisingly quickly and readily. Yields are obtained thereby which are nearly quantitative with regard to the xanthate as well as to the persulphate. The reaction, besides, does not very much depend on the degree of purity of the parent materials. Even readily oxidizable impurities of the xanthate cause a correspondingly increased consumption of persulphate, but they do not disturb the formation of alkyl xanthic disulphide as such. Due to their better purity the alkyl xanthic disulphides obtained by the oxidation with the aid of persulphate are lighter in color than those obtained according to other processes. The ethyl xanthic disulphide (fusing point of 28 0.) obtained by this process has a very light color and, owing to its special purity, it solidifies already completely at room temperags ture.

When preparing these alkyl xanthic disulphides there can be started from sodium xanthates or potassium xanthates of any desired degree of purity as well as from impurified solutions of these salts and from any commercial persulphate. Generally a xanthate and a persulphate of the same alkali metal are preferably used, because the by-product then forms a uniform alkali sulphate, for instance according to the equation Potassium ethyl potassium -9 potassium +ethyl xanthic The course of the reaction is independent from the fact whether solid or dissolved persulphates are used as starting materials.

The alkyl xanthic disulphides formed are insoluble in water and of higher specific weight than water; therefore they may readily be eliminated from the solution.

The products are to be used as collectors in flotation processes and as accelerators in rubber vulcanization.

The following examples serve to illustrate invention, but they are not intended to limit it thereto:

1. 200 grams of potassium ethyl xanthate with a content of 94.5 per cent. of xanthate are dissolved in water, the solution is filtered and filled up to 1000 cc. Into this solution 163 grams of potassium persulphate of 98 per cent. strength are gradually poured in. The alkyl xanthic disulphide is separated and the sulphate solution is evaporated. There are thus obtained 140.4 grams of ethyl xanthic disulphide (corresponding to a yield of 98.3 per cent. of the theoretical) and. 204 grams of potassium sulphate (corresponding to a yield of 99.5 per cent of the theoretical). The yields are calculated upon the parent quantities of pure potassium ethyl xanthate.

2. A solution of 100 grams of pure ammonium persulphate in 200 cc. of water is poured into a filtered solution of 146 grams of commercial sodium ethyl xanthate with a content of 86.4 per cent of anhydrous xanthate in 400 cc. of water, While agitating and cooling with water. After having been allowed to stand for a short time, the yellowish alkyl xanthic disulphide formed is eliminated from the solution. There are obtained 105.0 grams of ethyl xanthic disulphide, i. e. a yield of 98.9 per cent. calculated upon the ammonium persulphate used.

3. 120 grams of potassium iso-amyl xanthate of 98 per cent. strength are dissolved in 600 cc. of water and 81 grams of potassium persulphate of 98 per cent. strength are added, while cooling with water. The iso-amyl xanthic disulphide obtained is eliminated from the solution. The yield is 93.0 grams, i. e. 98.0 per cent. calculated upon the Xanthate used or 97.0 per cent. calculated upon the potassium persulphate.

I claim:

1. A process of preparing alkyl xanthic disulphides which comprises oxidizing xanthates of alkali metals in an aqueous solution by means of persulphates.

2. A process of preparing ethyl xanthic disulphide which comprises pouring 163 grams of potassium persulphate of 98 per cent. strength into 1000 cc. of a filtered solution containing 200 grams of potassium ethyl Xanthate of 94.5 per cent. strength in water, separating the ethyl xanthic disulphide and evaporating the sulphate solution.

3. A process of preparing ethyl xanthic disulphide which comprises pouring a solution of 100 grams of pure ammonium persulphate in 200 cc. of water into a filtered solution of 146 grams of commercial sodium ethyl xanthate with a content of 86.4 per cent. of anhydrous xanthate in 400 cc. of water, While agitating and cooling with water, allowing the mixture to stand for a short time and separating the yellowish ethyl xanthic disulphide formed from the solution.

4. A process of preparing iso-amyl xanthic disulphide which comprises dissolving 120 grams of potassium iso-amyl Xanthate of 98 per cent. strength in 600 grams of water adding 81 grams of potassium persulphate of 98 per cent. strength, while cooling with water, and separating the isoamyl xanthic disulphide formed from the solution.

AUGUST MOELLER. 

